Transversely flexible corrugated paper



March 17, 1942. I D, H, PLEWES ,ET AL. I 2,276,737 4 TRANSVERSELY FLEXIBLE CORRUGATED PAPER Filed June 24, 1939 W MTV- Patented Mar. 17, 1942 2,276,737 v TRANSVERSELY FLEXIBLE CORRUGATED PAPER David Harcourt Plewe s and Bernard Fox, To-

ronto, Ontario, Canada, assignors to Dominion Corrugated Paper Com Ontario, Canada pany Limited, Toronto,

Application June 24, 1939, Serial No. 281,024

4 Claims.

This invention relates to transversely flexible corrugated paper, and more particularly to corrugated paper which is faced on at least one surface with a ply of plane material.

Corrugated paper for wrapping purposes has been used for many years, but is open to the objection that it is not readily flexible in a direction transverse to the ribs or corrugations. Where bending is to take place on a predetermined definite line or lines bending or folding may be efiected by cutting or creasing along a straight edge or by making preformed creases or cuts along the line at which the bending is to take place. Also, sheets of corrugated paper have been made which may be bent transversely at any desired place by forming closely spaced cuts or depressions in the ribs. Applying the depressions to the sheet tends to flatten the corrugations, thus reducing the thickness of the sheetso that, such sheets are weakened so far as resistance to vertical pressure is concerned, and are also marked in such a manner as to adversely affect the appearance of the same. In commercial practice a heavier facing sheet is sometimes used to compensate for the loss of strength of the corrugations.

The object of the present invention is to devise a sheet which will be sufiiciently flexible to permit transverse bending or folding at any desired place on the sheet either diagonally of the length of the ribs or at right angles thereto, while retaining the normal thickness and appearance of the sheet with a minimum loss of strength to the sheet.

The object of this the corrugated sheet hereinafter described and illustrated in the annexed drawing. A method and apparatus for producing the sheet is also shown. In the drawing Fig. 1 is an end elevation of a sheet of corrugated paper made in accordance with this invention;

Fig. 2 a plan View of the same sheet slightly curved lengthwise of the rib to indicate the nature of the lines of weakness formed therein;

Fig. 3 a cross sectional View taken on the lines 3-3 in Figure 2;

Fig. 4 a longitudinal sectional view on the line 4-5 in Figure 2;

Fig. 5 a diagrammatic plan view of apparatus for making the sheet; and

Fig. 6 a side elevation of the apparatus shown in Figure 4.

In the drawing corresponding numerals in the different figures refer to corresponding parts.

invention is attained by ferred method of making the sheet 2, 3, and 4. The

The corrugated sheet I consists of a plurality of longitudinal ribs l and a facing sheet l adhesively secured to one side thereof. The preis by progressively bending it along a line first diagonally across the ribs in one direction and thendiagonally across the ribs in a substantially opposite direction to form a multiplicity of diagonal transverse lines of weakness therein throughout their length. Preferably the first bending is at sub,- stantially 45 to the length of the ribs in'one direction and the second bending is at substantially 45 in the other direction, although bending at angles of 30 and respectively or at other angles may be effective. Alternatively the sheet may be subjected to a single transverse bending at right angles to the length of the ribs, in which case the lines of weakness would run across the rib substantially at right angles thereto; but the product so made is inferior to that illustrated inasmuch as it is not so flexible, particularlyfor diagonal bending of the sheet, and moreover the method is more difficult to perform inasmuch as rupture of the paper may occur, thus weakening the sheet. In carrying out the process the corrugatedsheet is moved forward and sharply bent transversely of the ribs during its course of travel. The sheets are bent inwardly towards-the corrugated side, since to bend them toward the facing side would rupture the corrugations.

As will be seen from Figure 1 when a sheet of corrugated paper I made in accordance with this inventionis laid out flat the ribs are of the same fully rounded shape as in ordinary corrugated paper so that the sheet presents substantially the same appearance as any ordinary sheet of corrugated paper, although on close inspection even in its-flat form the corrugations or ribs l will be seen to bear on their surfaces barely discernible lines, which represent the lines of weakness which have been formed therein by the process above described. When a sheet made in accordance with the preferred method above described is curved longitudinally of the ribs l thus forming a transverse bend in the ribs, these lines of weakness form a multiplicity of closely spaced wrinkles I in substantially the form illustrated in Figures wrinkles are somewhat irreguwould depend somewhat on the the sheet is made, the amount lar and their form material of which of bending which tension under which the bending takes place, but in general, when the sheet is curved or folded as in Figures 2, 3, and 4, the wrinkles l are substantially V-shaped formed on the sides of the they are subjected to, and the ribs by lines extending diagonally of the ribs from the bottom of the troughs between the ribs and meeting on either side of the apex thereof.

These wrinkles occur along the lines of weakness formed in the sides of the ribs and the wrinkles on opposite sides do not quite coincide, so that when the sheet is curved or folded transversely of and at right angles to the ribs, the sides of the ribs on the line or lines of curving or bending collapse inwardly causing the apex or top of the rib to take on an irregular zig-zag formation. The lines of weakness are not uniformly spaced but when the sheet is curved as illustrated the wrinkles which are thereby formed show that they occur throughout the length of the ribs approximately one quarter to one-half inch apart.

Figures 5 and 6 show diagrammatically means for effecting the desired bending of the material. The material is preferably in the form of along sheet or strip which may be fed to the apparatus directly from the corrugating machine or which may be wound on a roll 2 and carried from such rollthrough guide rollers 3 and 4 to and over a supporting bar or roller 5 and down and around a deflecting and bending bar 6 and then over another supporting bar or roller 1 to and around the guide roller 8 and back under the supporting roller 1 and around a deflecting and bending bar 8' and then down and under the bar or roller 5 to another guide roller 9 and from thence to a rewind roller I which may be positively driven to draw the sheet through the apparatus. The roller 2 and any of the guide rollers or supporting rollers may be positively driven, but it is essential that the strip be under tension when passing around the bending bars. Instead of utilizing the rollers and T for the transverse bending in the opposite direction from the first transverse bending, another set of supporting rollers and bending bar may be used and may be in the same plane as the first rollers and bendin'g bar or above or below them.

It will be seen that a sharp bending action is produced by the apparatus described above. The corrugations are preferably on the upper side of the sheet as shown in Figure 5 and extend across the sheet or strip. The pull of the sheet around the bending bars 6 and 6 form wrinkles which result in linesv of weakness. When the sheet is passed over the roller I after passing under the bending bar 8 and when it is passed under the roller 5 after passing around the creasing bar 6 the wrinkles formed by the bar straighten out so that the treated sheet has a normal appearance unless closely examined or unless bent transversely of the length of the ribs.

'It is to be understood that in the specification and claims the word transversely used in reference to the ribsor corrugations is not, of course,

limited to a direction at right angles to the length of the ribs, but applies also to a direction diagonally across the ribs.

What we claim as our invention is:

1. A transversely flexible sheet of corrugated paper, faced on one surface with a ply of plane material, the ribs of said sheet having a multiplicity of transverse lines of weakness along the sides thereof, said ribs being normally of ordinary contour and shape but adapted to crease along said lines of weakness when the sheet is bent or folded transversely of the ribs.

2. A transversely flexible sheet of corrugated paper, faced on one surface with a ply of plane material, the ribs of said sheet having a multiplicity of closely spaced lines of weakness extending transversely of the sides of the ribs from points adjacent the bottom of the troughs between the ribs to points adjacent the apices of the ribs, said ribs being normally of ordinary contour and shape but adapted to crease along said lines of weakness when the sheet is bent or folded transversely of the ribs.

3. A transversely flexible sheet of corrugated paper, facedj on one surface with a ply of plane material, the ribs of said sheet having a multiplicity of closely spaced lines of weakness extending diagonally and transversely of the sides of the ribs from points adjacent the bottom of the troughs between the ribs to points adjacent the apices of the ribs, the lines of weakness extending diagonally in different directions on the same side of each rib meeting at one side of the apex of the rib, said ribs being normally of ordinary contour and shape but adapted to crease along said lines of weakness when the sheet is bent or folded transversely of the ribs.

4. A transversely flexible sheet of corrugated paper, faced on one surface with a ply of plane material, the ribs of said sheet having a multiplicity of closely spaced lines of weakness extending diagonally and transversely of the sides of the ribs from points adjacent the bottom of the troughs between the ribs to points adjacent the apices of the ribs, the lines of weakness extending diagonally in different directions on the same side of each rib meeting at one side of the apex of the rib, the meeting points of said lines of weakness on opposite sides of the ribs being slightly spaced longitudinally of the ribs, said ribs being normally of ordinary contour and shape but the sides ofthe ribs'being adapted, when the sheet is bent or folded transversely of and at right angles to the ribs, to collapse inwardly causing the apex or tops of the ribs at the point of bending to take on an irregular zig-zag formation.

DAVID H. PLEWES. BERNARD FOX. 

